faressoft

DOM Performance

• How the browser renders the document
  • Receives the data (bytes) from the server.
  • Parses and converts into tokens (<, TagName, Attribute, AttributeValue, >).
  • Turns tokens into nodes.
  • Turns nodes into the DOM tree.
• Builds CSSOM tree from the css rules.

paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent